I have a 97 540i with 180K miles. Never had any serious problems until I started getting the classic "Smoke on Startup" problem. Did lots of research on the forums that led me to the OSV.
I originally replaced the OSV without removing the intake manifold, what a pain. When I inspected the orange diaphragm, it didn't have the rips that were common with others. After the replacement was done I would hear the diaphragm vibrating, holding my hand on the back of the manifold would quiet it.
Thinking I didn't do something right the next step was to remove the intake manifold. It was full of oil. While this was out I replaced the "cyclone valve" behind the timing chain cover, the various pipes and tubing under the manifold, intake gaskets and all the o-rings that were accessible. Put it all back together and it started and ran fine, for about 2 weeks. Then another Smoke on Startup.
So now thinking I may have installed a bad OSV I replaced just the rubber diaphragm (following instructions from another thread) by popping just the cap off.
Now I have a vibrating diaphragm again and still get the frequent smoke on startup.
I'm out of ideas, any clues??